1. Field of the Invention
The present invention relates to digital recording/playback, and more particularly, to error correction of a digital recording/playback apparatus for recording/playing MPEG-2 (Moving Picture Experts Group) signals.
2. Description of the Related Art
A digital video apparatus can be applied to various fields such as communications, including teleconferencing and video phones, computers, or household electronic appliances. For example, a digital recording/playback apparatus such as a digital video cassette recorder (to be referred to as a D-VCR hereinafter) or a digital video cassette (DVC: to be also called a camcorder) adopts the MPEG-2 standard for digital storage media.
According to the MPEG-2 standard, a program stream consists of the respective elementary streams for video, audio and user data, and is packetized into a packetized elementary stream (PES).
Generally, a picture transmitted from a broadcast station consists of a PES, and one PES is transmitted in units of a predetermined number of transport packets. Additionally, data on a transmission path is in a system layer structure based on the MPEG-2 standard. The system layer structure has a packet structure in units of 188 bytes. In each packet, a 4-byte header is divided into 1-byte sync and 3-byte side information. The number of bytes of the header can vary. The region of the packet, excluding the header, contains video data, audio data or user data.
When recording MPEG-2 bit streams, a digital recording/playback apparatus extracts trick play data from the MPEG-2 bit streams as well as normal play data to satisfy both a normal-play (NP) mode and a trick-play (TP) mode, and records the extracted trick play data on a separate trick play data region.
Also, a digital recording/playback apparatus can record an ATV (Advanced Television) signal which is an American type of HDTV (High Definition Television) signal, or a DVB (Digital Video Broadcasting) signal which is an European type of HDTV signal, both of which adopt MPEG-2 compression. The digital recording/playback apparatus records the signal in a 25, 12.5 or 6.25 Mbps recording mode according to the bit rate of a transmitted signal. If there is a difference between the bit rate of a recording mode and that of the transmitted signal, a stuffing region is allocated to a predetermined region of the normal play data region, thereby recording stuffing data, i.e., dummy data. In performing error correction coding and decoding in consideration of the stuffing data, the capability of correcting errors of normal play data is affected by the quantity of the stuffing data. The present invention has been proposed to improve the capability of correcting errors of normal play data, without being affected by the stuffing data which is the dummy data.
Also, when the video bit stream of an MPEG-2 format is recorded by the digital recording/playback apparatus, an ECC (Error Correction Code) structure of a track format is for recording inter-picture coded bit streams. Thus, the inter-picture coded bit streams such as the ATV or DVB signal are susceptible to error.
To solve the problem, a predetermined region of the normal play data region is allocated, called an ECC3 region, for storing outer parity for correcting errors of only the normal play data.
However, in performing error correction coding using the additionally provided ECC3 region, the normal play data of the ECC structure is written in units of a predetermined number (10 typically) tracks and the outer parity is added to the ECC3 region to allow interleaving to correct burst errors. This requires a large capacity memory. In practice, decoding the ECC3 requires complicated hardware.
To solve the above problems, it is a first objective of the present invention to provide a digital recording/playback apparatus for performing outer error correction coding by arranging a predetermined pattern data in a stuffing region and a trick play data region for an ECC block containing the stuffing region, during a recording mode, and performing outer error correction decoding by arranging the pattern data used in the coding is in the stuffing region and the trick play data region, during a playback mode.
It is a second objective of the present invention to provide a digital recording/playback apparatus for performing outer error correction coding by arranging a predetermined pattern data in an ECC3 region additionally provided in the normal play data region, during a recording mode, and performing outer error correction decoding by arranging the pattern data used in the coding in the ECC3 region, during a playback mode.
It is a third objective of the present invention to provide a digital recording/playback method for performing outer error correction coding by arranging a predetermined pattern data in a stuffing region and a trick play data region for an ECC block containing the stuffing region, during a recording mode, and performing outer error correction decoding by arranging the pattern data used in the coding in the stuffing region and the trick play data region, during a playback mode.
It is a fourth objective of the present invention to provide a digital recording/playback method for performing outer error correction coding by arranging a predetermined pattern data in an ECC3 region additionally provided in the normal play data region, during a recording mode, and performing outer error correction decoding by arranging the pattern data used in the coding in the ECC3 region, during a playback mode.
Accordingly, to achieve the first objective, there is provided a digital recording/playback apparatus for recording normal play data and trick play data separately on a recording medium in a predetermined data format, and reproducing the data recorded on the recording medium, the apparatus comprising: an adding unit for adding extra information indicative of a decoding timing to a received transport stream and outputting the normal play data in units of a predetermined number of sync blocks; an extracting unit for extracting the trick play data from the received transport stream and outputting the trick play data in units of a predetermined number of sync blocks; an arranging unit for arranging the normal play data in a normal play data region, the trick play data in a trick play data region, and predetermined pattern stuffing data in a stuffing region of the normal play data region according to a difference between a predetermined recording rate and a bit rate of the transport stream; an error correction coder for performing outer error correction on the normal play data, regardless of the trick play data and stuffing data among the arranged data, and outputting error-correction-coded data; and a modulator for modulating the error-correction-coded data and transmitting modulated data to the recording medium.
Here, the error correction coder comprises: an outer error correction coder for arranging a predetermined pattern data in the stuffing region and the trick play data region, adding an outer parity to the normal play data, and outputting outer-error-correction-coded data; and an inner error correction coder for adding an inner parity to the outer-error-correction-coded data output from the outer error correction coder, and outputting inner-error-correction-coded data.
Also, the digital recording/playback apparatus further comprises: a demodulator for demodulating the data recorded on the recording medium and outputting demodulated data; an error correction decoder for performing error-correction-decoding on the demodulated data; and a selector for selecting error-correction decoded normal play data during a normal play mode, and selecting error-correction decoded trick play data during a trick play mode, according to a normal/trick play mode signal, wherein the error correction decoder comprises: an inner error correction decoder for performing inner error correction decoding on the demodulated normal play data using the inner parity during a normal play mode and outputting inner-error-correction-decoded normal play data to the selector, and for performing inner error correction decoding on the demodulated trick play data using the inner parity during a trick play mode and outputting inner-error-correction-decoded trick play data to the selector; and an outer error correction decoder for arranging the predetermined pattern data used in the error correction coding in the stuffing region and the trick play data region, performing outer error correction decoding on the inner-error-correction-decoded normal play data using the outer parity, and outputting outer-error-correction-decoded data.
To achieve the second objective, there is provided a digital recording/playback apparatus wherein an outer error correction coder performs outer error correction coding by overwriting the predetermined pattern data in a separate error correction code region of the normal play data region, and an outer error correction decoder performs outer error correction decoding by overwriting the predetermined pattern data in a separate error correction code region of the normal play data region.
To achieve the third objective, there is provided a method for recording normal play data and trick play data separately on a recording medium in a predetermined data format, and reproducing the data recorded on the recording medium, comprising the steps of: (a) adding extra information indicative of a decoding timing to a received transport stream and outputting a transport packet to which the extra information is added; (b) mapping a first predetermined number of transport packets, to which the extra information is added, in units of a second predetermined number of sync blocks and outputting the normal play data; (c) extracting trick play data from the received transport stream; (d) packetizing extracted trick play data, mapping the first predetermined number of transport packets of packetized trick play data in units of the second predetermined number of sync blocks and outputting the trick play data; (e) arranging the normal play data in a normal play data region, the trick play data in a trick play data region, and predetermined pattern stuffing data in a stuffing region of the normal play data region according to a difference between a predetermined recording rate and a bit rate of the transport stream; (f) performing outer error correction on the normal play data, regardless of the trick play data and stuffing data among the arranged data, and outputting error-correction-coded data; and (g) modulating the error-correction-coded data and transmitting modulated data to the recording medium.
Here, the step (f) comprises the steps of: (f1) arranging a predetermined pattern data in the stuffing region and the trick play data region, adding an outer parity to the normal play data, and outputting outer-error-correction-coded data; and (f2) adding an inner parity to the outer-error-correction-coded data, and outputting inner-error-correction-coded data.
Also, the method further comprises the steps of: (h) demodulating the data recorded on the recording medium and outputting demodulated data; (i) performing error-correction-decoding on the demodulated data; and (j) selecting error-correction decoded normal play data during a normal play mode, and selecting error-correction decoded trick play data during a trick play mode, according to a normal/trick play mode signal, wherein the step (i) comprises the steps of:
(i1) performing inner error correction decoding on the demodulated normal play data using the inner parity during a normal play mode and outputting inner-error-correction-decoded normal play data, and performing inner error correction decoding on the demodulated trick play data using the inner parity during a trick play mode and outputting inner-error-correction-decoded trick play data; and
(i2) arranging the predetermined pattern data used in the error correction coding in the stuffing region and the trick play data region, performing outer error correction decoding on the inner-error-correction-decoded normal play data using the outer parity, and outputting outer-error-correction-decoded data.
To achieve the fourth objective, according to the present invention, in the step (i2), outer error correction decoding is performed by overwriting the predetermined pattern data used during the error correction coding in a separate error correction code region of the normal play data region.